St. Louis, June 8, 2001--New research shows that PET scans can often identify which women with advanced breast cancer are likely to respond to hormone therapies such as tamoxifen.

"Using PET scans, we were able to predict within two weeks who was responding to hormone therapy," said Joanne Mortimer, M.D., professor of medicine at Washington University School of Medicine. "That is very significant. If doctors could tell within two weeks that someone will respond to hormone therapy, they will be less likely to prescribe chemotherapy for those patients."

The study, led by Mortimer, of the Siteman Cancer Center at Washington University and Barnes-Jewish Hospital, is published in the June 1 issue of the Journal of Clinical Oncology.

Hormone therapy is kinder and gentler to patients than chemotherapy, and is usually just as effective. But according to Mortimer it is greatly under-used by physicians. Often, this is because the therapy initially produces symptoms of tumor growth, so doctors can't tell whether a woman is responding normally to the treatment or whether her cancer is progressing.

The problem occurs because hormone therapy stimulates breast tumors to flare up and grow a bit before causing them to shrink. This can result in pain at tumor sites and in elevated tumor markers in the blood. This "flare reaction" is physically experienced by about one in 20 women with advanced breast cancer who receive hormone therapy. At the same time, it is also known that women who experience a clinically detectable flare reaction respond to hormone therapy.

"We proposed that all patients who eventually respond to hormone therapy have a temporary flare reaction, but that it occurs subclinically in most cases," said Mortimer. The researchers further proposed that this subclinical flare could be detected using positron emission tomography (PET). PET measures the functional activity of normal and diseased tissues in the body.

Mortimer's study involved 40 women (average age 58) with advanced breast cancer and estrogen-receptor-positive tumors. Estrogen receptors must be present in breast tumor cells for hormone therapy to work. "Most cases of breast cancer are estrogen-receptor positive," said Mortimer, "but only 30 to 60 percent of them will likely benefit from hormone therapy." The goal of Mortimer's study was to identify whether a particular woman with breast cancer fell among the fraction that would be helped.

Each woman in the study received two PET scans before tamoxifen therapy began and two more seven to 10 days after therapy was initiated. In the end, 21 patients (52 percent) responded to the therapy. These women showed either tumor shrinkage or no progression. The remaining 19 patients experienced tumor progression.

The researchers then looked back at the PET scans from the women. The images revealed a highly statistically significant increase in the metabolic activity--a flare reaction--in tumors from women who responded to the therapy compared to the women who didn't respond.

Though a larger study must verify these findings, said Mortimer, "this study strongly suggests that PET can predict whether a woman with advanced estrogen-receptor positive breast cancer will benefit from tamoxifen therapy. And that should help improve the quality of life for these patients."

Funding from the National Institutes of Health supported this research.

The full-time and volunteer faculty of Washington University School of Medicine are the physicians and surgeons of Barnes-Jewish and St. Louis Children's hospitals. The School of Medicine is one of the leading medical research, teaching and patient-care institutions in the nation. Through its affiliations with Barnes-Jewish and St. Louis Children's hospitals, the School of Medicine is linked to BJC Healthcare.
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